This invention is related to the use of sensors applied to the body for monitoring or making measurements of body tissue condition, metabolism or other body functions indicative of health. More specifically, the invention is directed to an appliance which can be readily attached to the body to support a sensor adjacent thereto in a stable disposition for accurate and precise measurements unhampered by artifact due to sensor motion relative to the body.
One application for a sensor appliance of the type described herein is in pulse oximetry, a non-invasive method of measuring the relative oxygen saturation of the blood. Pulse oximeters generally employ light sources, e.g., light emitting diodes (L.E.D.s), to alternately direct light of two different wave lengths, e.g., red and infra-red, to the blood through the skin. The light transmitted or reflected by the blood at the different wave lengths can then be compared to provide a measurement of oxygen saturation.
Typically, a sensor appliance containing the light sources, e.g., L.E.D.s, and a light sensor, e.g., photodetector, is mounted on the finger, toe or ear lobe. An example of such a sensor is disclosed in European patent application No. 84302994.3 for a Sensor having Cutaneous Conformance. In prior art sensor appliances, individual L.E.D.s and a photodetector of an oximeter sensor are each mounted on a respective rigid substrate which is, in turn, incorporated into a flexible envelope, making for a bulky device which often result in unstable readings due to limited conformability when attached to a patient. In addition to yielding unstable readings due to limited conformability, prior art appliances are subject to contamination and suitable for use only as disposable devices since their discrete LED and photodiode components and wiring are relatively bulky and vulnerable to external contaminants. Moreover, such appliances cannot be readily cleaned for use on multiple patients. Flexibility in the areas of the light sources and detectors is minimal thereby preventing good conformance with small toes, fingers and earlobes as in the case of neonates. In addition, disassembly of and/or damage to the structure of prior art appliances often results from attempts at repeated usage.